A temperature sensor for detecting temperature of liquid according to a prior art is disclosed in Japanese Unexamined Utility Model Application Publication No. H03-39125. This sensor 100 is shown in FIG. 3. The sensor 100 is disposed in the liquid so as to detect the temperature of the liquid. The sensor 100 includes a temperature detector 120 connecting to a pair of electric wires 140. The wires 140 extend from a casing 110 of the sensor 100 to the outside of the casing 110. The wire 140 is composed of a lead wire 140a coated with an insulation tube 140b. The wire 140 connects to the detector 120 at a connection portion 130.
However, the liquid may penetrate into the connection portion 130, so that two wires short-circuit. Therefore, organic sealant is filled in the casing 110 so that a mold portion 150 is formed between the casing and the detector 120 or the wires 140. Since the mold portion 150 is formed, two distances L3, L4 between two connection portions become long. Each distance L3, L4 is defined as a distance between the connection portions 130 along with the wires 140, respectively. Therefore, even if the liquid penetrates between the mold portion 150 and the insulation tube 140b, the wires 140 disposed between the connection portions 130 do not short-circuit easily since the distance L3, L4 is long. Here, the organic sealant is made of thermosetting resin such as epoxy resin, so that the mold portion 150 is formed with injecting the resin into the casing 110.
However, the insulation tube 140b may be deformed in some cases such as sudden temperature change. The mold portion 150 adheres to the insulation tube 140b, so that the mold portion 150 may crack or be damaged because of the deformation of the insulation tube 140b. Then, the liquid may penetrate through the crack into the insulation tube 140b, so that the wires short-circuit or the mold portion 150 flows out into the liquid as a detection object.